Table 1.

Quality assessment using the Methodological Index for Nonrandomized Studies.

Study	1	2	3	4	5	6	7	8	9	10	11	12	MINORS score
Kim et al., 2005 [19]	2	2	2	2	2	2	2	2	1	2	0	2	21
Kwok et al., 2005 [25]	2	1	2	2	2	2	2	2	0	2	2	2	21
Liu and Mori., 2005 [24]	2	2	2	2	2	2	2	2	1	2	0	2	21
Lee and Kim, 2010 [18]	2	2	2	2	2	2	2	2	1	2	0	2	21
Pournaras et al., 2011 [17]	2	2	2	2	2	2	2	2	0	2	0	2	20
Chang et al., 2013 [23]	2	2	2	2	2	1	2	2	1	0	2	2	20
Oh et al., 2013 [16]	2	2	2	2	2	2	2	2	0	2	0	2	20
Ahn et al., 2014 [22]	2	2	2	2	2	2	2	2	1	2	0	2	21

(1) A stated aim of the study; (2) inclusion of consecutive patients; (3) prospective collection of data; (4) endpoints appropriate for the study aim; (5) unbiased evaluation of endpoints; (6) follow-up period appropriate to the major endpoint; (7) loss to follow-up not exceeding 5%; (8) a control group having the gold standard intervention; (9) contemporary groups; (10) baseline equivalence of groups; (11) prospective calculation of the sample size; (12) statistical analyses adapted to the study design.

0: not reported; 1: reported but inadequate; 2: reported and adequate.